The purpose of this study is to describe and improve the utilization of screening mammography by primary care physicians in asymptomatic women in two age groups: age 35-49 and 50-75 years. OBJECTIVES: The specific objectives are: (1) to describe primary care physician performance of screening mammography in a randomly selected group of practices in family medicine; (2) to identify factors associated with differences in primary care physician decision policies and practice; and (3) to test the efficacy of an educational intervention based on physician decision policies in improving physician breast cancer screening practice. RATIONALE: Mammographic screening for breast cancer in asymptomatic women significantly decreases breast cancer mortality. Physician utilization of screening mammography is markedly less then recommended. However, little is known about the clinical decision policies which physicians apply, the factors determining these practices, and the effective means of improving practice. In other contexts of medical care, educational interventions based on clinical decision policy feedback have been more effective in modifying practice than more traditional educational interventions. DESIGN AND METHODS: With regard to the first two objectives, 60 physician practices will be randomly selected from two defined regions in the State of Washington (Cross-Sectional Study). Physician practice, clinical decision policies, knowledge, attitudes, risk preferences, and-practice characteristics will be measured. Practice will be examined by medical record reviews of 20 female patients in two age groups, 35-49 and 50-75 years, who were seen over the prior two months at each practice. The content and variation of physician practice and internal decision policies will be described. With regard to the third objective, 236 physician practices will be randomized to one of two educational interventions and one control group (Intervention Study): an individualized decision policy feedback program plus knowledge-based education; a knowledge-based education alone; and no intervention. Pre- and post-intervention measurements of practice, decision policies, knowledge, attitudes, risk preference, and practice characteristics will be completed. Changes after 6 months will be examined. SIGNIFICANCE: The products will be an effective and needed means of characterizing and improving primary care physician mammographic screening practices and policies in female patients, age 35-49 and 50-75 years.